Rotary pumps of the non-centrifugal type



Nov. 26, 1957 F. w. MOCOMBIE ROTARY PUMPS OF THE NON-CENTRIFUGAL TYPE 2Sheets-Sheet 1 Filed March 15, 1954 INVENTOR fFPQE/P/c/rMz P/VcCO/VBMNov; 26, 1957 F. w; MQCOMBIE 2,814,256

v ROTARY Pumps OF THE NON-CENTRIFUGAL TYPE Filed March 15. 1954 v 2Sheets-Sheet 2 FIG-.3.

INVENTOR United States Patent C F ROTARY PUMPS on THE NON-CENTRIFUGALTYPE Frederick Walter McCombie, London, England, assignor to MegatorPumps & Compressors Limited, London, England Application March 15, 1954,Serial No. 416,006

Claims priority, application Great Britain March 24, 1953 8 Claims. (Cl.103-463) This invention relates to rotary pumps of the noncentrifugaltype, examples of such pumps forming the subject of our prior U. S.Patents Nos. 2,561,808; 2,561,809; 2,561,810; 2,612,846; 2,728,615 and2,750,896. Such pumps include as working parts a displacement chambergenerally referred to as a shoe containing an eccentrically mounted discwhich is rotatably mounted therein to impart a reciprocating movement tothe shoe in the plane of rotation of the disc to open and close inletand outlet ports in a port plate over which the shoe slides and toprovide the necessary displacement effect, the disc engaging the wallsof the shoe at two oppositely disposed points on its periphery and alsoat the sides to provide a substantially fluid tight seal, the shoe andits associated disc being carried by a driving shaft mounted within theouter casing, the shoe being situated on the high pressure side of thepump, the pressure of the fluid being pumped serving to maintain theshoe in a fluid tight connection with the port plate with which it isslidably associated. Such pumps include either a single shoe or aplurality thereof, for example, three and the chief object of thepresent invention is to reduce the bending moment in the disc carryingshaft generally referred to as the rotor shaft resulting from the sidethrust imposed on the shaft by each disc during its working stroke owingto the difference in fluid pressure between the inside and outside ofthe shoe.

In this connection it will be appreciated that it is desirable, ifpossible, to avoid the use of an intermediate hearing or bearings forthe rotor shaft but in the case of a pump which includes, for example,four or more shoes and utilising only two bearings at opposite ends ofthe shaft the length of shaft which is unsupported is quite long.

A rotary pump of the non-centrifugal type including a plurality of shoeseach mounted for reciprocating movement over a port plate under theaction of an eccentric disc, all the eccentric discs being associatedwith a common shaft is characterised according to the invention in thatthe shoes are so positioned around the axis of the shaft as to balanceout or substantially balance out any bending forces to which the shaftis subjected during operation.

It is preferred that the shoes shall be so arranged that some of themlie on one side of the shaft the remainder being arranged on theopposite side, the shoes on opposite sides facing in diametrallyopposite directions.

It is, however, within the scope of the invention to arrange the shoesin any other way which will produce the desired result. For example, theshoes on one side of the shaft may be arranged at an angle with respectto the shoes on the opposite side, the angle being a large one andbetween 90 and 180 so that the bending forces on the shaft will bebalanced out to a substantial extent.

As a further alternative the shoes may be equidistantly spaced about theaxis of the shaft although such an arrangement might lead todifficulties in construction.

2,814,256 Patented Nov. 26, 1957 It is preferred to use four or sixshoes arranged in pairs. In the case of four shoes being employed, onepair will be arranged on one side of the shaft and the other pair willbe arranged on the opposite side. If six shoes are used then one pair,for example, the central pair, will be arranged on one side, whilst theoutside pairs will be arranged on the opposite side.

It is preferred that the discs comprising each pair shall beeccentrically arranged in diametrally opposite directions and that allthe discs associated with the rotor shaft shall be arranged in equallyspaced angular positions about the axis of the rotor shaft.

When arranging the discs as pairs each pair may be associated with acommon port plate, the plate being formed with two sets of ports forco-operating with each shoe.

It will be appreciated that when using two oppositely facing shoes or inan arrangement in which one or more sets of shoes face the opposite wayto the remaining set or sets, two oppositely positioned port plates willbe required which will be situated in the pump casing on opposite sidesof the rotor shaft, the port plates being staggered lengthwise of theshaft. It is found in practice that this part or complete balancing ofthe bending forces or side thrust on the rotor shaft enables a shaft tobe constructed of smaller diameter, this in turn permitting of greatereccentricity of the discs of a particular diameter, the total elfectbeing to produce a lighter and cheaper rotor for a given capacity andpressure. This construction also reduces the resultant side thrust onthe bearings of the rotor so cheapening the bearings and reducingfriction and wear.

Furthermore it obviates the necessity or desirability of supporting theshaft between its ends by intermediate bearings even though the shaftmay be of considerable length.

It is found that the arrangement of six shoes described above greatlyreduces the shaft stresses as compared with an arrangement having allthe shoes facing the same way owing to the partial balancing of theforces involved. At the same time owing to the fact that four shoes faceone way and two the other way, the resultant side thrust on the rotorshaft is always in the same direction. This arrangement has theadditional advantage of helping to maintain the lubricating film in thebearings and enabling the rotor to run smoothly even though the bearingsare a very loose fit.

Referring to the drawings:

Figure 1 is a longitudinal vertical section of a pump in accordance withthe invention;

Figure 2 is a longitudinal horizontal section of the same;

Figure 3 is a cross-section.

The invention will hereinafter be described in detail as applied to apump which includes three pairs of shoes, namely a centrally positionedpair and two end pairs making six shoes in all.

In the construction illustrated the pump comprises a body or casing 1forming a pressure chamber 1 carrying at its end bearings 2 and seals 3for a rotor shaft 4 carrying eccentric discs 5, the rotor shaft carryinga coupling drum 6 through the medium of which the rotor shaft is drivenfrom a suitable source of power supply.

The casing carries three main covers 7 forming suction chambers 8 whichcommunicate with a common supply chamber 10 having an inlet 10 for theadmission of the liquid which is being pumped. The three main cov ers 7are also formed with discharge passageways 9 which communicate throughopenings 9' with the pressure chamher 1' which is provided with adischarge outlet (not shown), the pressure in the chamber 1' beinghigher than at the suction side.

Each disc revolves in a shoe 11 which is preferably composed of acomparatively resilient mouldable material such as a natural orsynthetic rubber or incorporates a lining composed of such material, theshoe fitting the disc on its opposite faces and also at two oppositepoints on its periphery. The arrangement is such that as a result ofrotation of the disc the shoe will be reciprocated vertically over theface of a port plate 12 carried by the adjacent cover 7.

Each port plate 12 is formed with two sets of laterally spaced suctionand discharge ports one set being provided for each shoe there being ineach set two suction ports 13 which communicate with the interior of thecover 7 and two discharge ports 14 which lead to the interior of themain body 1 of the pump. The pressure in the chamber 1, being higherthan the pressure in the ports 13 and covers 7, tends to hold all theshoes in good sealing engagement with the faces of the port plates 12.

Each shoe 11 is formed with a pair of ports 15 which perform thefunctions of both suction and discharge ports and communicatealternately with ports 13 and 14 under the reciprocating action of theshoe. The effective internal volume of the shoe is varied as a result ofrotation of the disc and consequently the shoe acts as a displacementchamber, the liquid being drawn into the interior of the shoe throughthe ports 13 and when ports 14 and 15 are in register being dischargedthrough ports 14 and into the chamber 1 from which it is finallydischarged.

The two discs 5 of the centre pair are arranged at 180 to one another,the two discs of each outer pair being also at 180 to one another andthe outer pairs at 120 and 240 respectively to the centre pair. Thisclearly places the six discs in equally-spaced angular positions withtheir working strokes occurring in regular sequence and results in asmooth displacement of fluid and an even turning moment.

This arrangement of six shoes has another advantage over the commonlyused design employing three shoes, namely, that there are two shoesfunctioning at every point in the cycle, whereas with three shoes at120, although the theoretical combined displacement curve is practicallyas smooth as with the six shoes, it is the resultant of two shoesfunctioning during parts of the cycle and only one shoe during otherparts. The actual displacement of the liquid is equivalent to thetheoretical combined displacement of the shoes less the leakage or slip,and this leakage is twice as great when two shoes are functioning aswhen one only is functioning. Thus the three shoe pump introduces inpractice an irregularity of flow that is absent from the six shoe pumpin which there are always two shoes functioning at one time.

The shoes shown are of the known type, as disclosed by thespecifications and drawings of the earlier patents hereinbefore referredto, each shoe being of substantially U shape and being cut away to clearthe rotor shaft, the limbs being connected by one or more bolts andtubular distance pieces.

I claim:

1. A rotary pump comprising a casing defining a pressure chamber and asupply chamber, a rotor shaft mounted in said casing and extendingthrough said pressure chamber, said casing including a plurality of portplates equally spaced from the axis 'of said shaft, the inner surfacesof said port plates having planar slideways and each having a suctionport in communication with said supply chamber and a discharge port incommunication with said pressure chamber, a plurality of discseccentrically mounted on said shaft within said pressure chamher, and ahollow shoe fitting each disc and engaging a slideway of one of saidport plates to be reciprocated thereover by rotation of the disc foralternate communication with said suction and discharge ports, each shoeclosely surrounding each disc diametrically thereof in a plane parallelto the respective slideway and forming a pumping chamber between theperiphery of the disc and the port plate, said port plates beingsubstantially equally spaced angularly around said shaft to distributethe thrust imposed on the shaft by each disc during its working strokeand reduce the bending moment in said shaft.

2. A rotary pump as set forth in claim 1 wherein each port plate isprovided with two sets of laterally spaced suction and discharge ports,one set for each shoe, each shoe having a pair of ports communicatingalternately with the suction and discharge ports of the plate.

3. A rotary pump as set forth in claim 1, wherein some of the shoes andport plates are arranged on one side of the shaft while the remainder ofthe shoes and port plates are arranged on the opposite side of theshaft.

4. A rotary pump as set forth in claim 1, wherein the shoes are arrangedin pairs spaced apart throughout the length of the shaft, so that theworking strokes occur in regular sequence and results in a smoothdisplacement of fluid and in even turning moment of the shaft.

5. A rotary pump as set forth in claim 4, wherein each pair of shoescooperate with a common port plate.

6. A rotary pump as set forth in claim 1, wherein the discs are arrangedin equally spaced angular positions about the axis of the shaft.

7. A rotary pump as set forth in claim 3, wherein the shoes are arrangedin three pairs, the central pair engagging port plates on one side ofsaid shaft and the two outside pairs engaging port plates on theopposite side of said shaft.

8. A rotary pump as set forth in claim 3, wherein the shoes are arrangedin pairs along the length of the shaft, one pair of shoes engaging portplates on one side of said shaft and another pair of shoes engaging portplates on the opposite side of said shaft.

References Cited in the file of this patent UNITED STATES PATENTS

